This invention relates to a shaft coupling.
Various kind of shaft couplings such as universal joint, ball joint or Oldham's joint suitable for the conditions imposed upon the driving shaft and the driven shaft have been proposed.
However these improvements of shaft couplings have been confined to the joint mechanism between driving shaft and driven shaft. No improvement has been done with the connections between shafts and shaft coupling.
Typical connection between shafts and shaft coupling is a key-fixation connection or a bolt-fixation connection. The key-fixation connection comprises key-grooves shaped on the outer surface of the shaft and on the inner surface of the cylindrical part of shaft coupling, and a key to be penetrated into the space formed by the key grooves. The key-fixation connection has widely used in various kind of machines. However the key-fixation connection has defaults that processing of key grooves is difficult work and that backlashes between shafts and shaft coupling are liable to occur when the shafts rotate in reciprocal directions.
The bolt-fixation connection comprises a shaft, a cylindrical part with a radially-bored bolt hole and a fixation bolt penetrating in the bolt hole and pushing a side point of the shaft. This connection is free from the difficulty of processing and the occurrence of backlashes. However the bolt-fixation connection has another difficulty-eccentricity. Because the shaft is pushed by the fixation bolt along a radial direction in the cylindrical part, the shaft center deviates from the center of the cylindrical part. In addition to the eccentricity between the shaft and the cylindrical part, another eccentricity is derived from the aberrance of center of gravity of the cylindrical part, because the cylindrical part has a single fixation bolt along a radius.
Because of the two eccentricities, the center of gravity of shaft coupling deviates from the center of driving shaft or driven shaft. The deviation of centers will induce strong transversal vibrations of shaft coupling when the shafts rotate at high speed.